Hallo,
Our boar is between 5 and 6 years old. He is straining hard to defecate, it is clearly painful and he is spending a lot of time standing still, twitching his tail, with his anus protruding. His droppings are a little small and tight, but not abnormally so. He is eating and drinking enthusiastically and there is no blood or pus or strange smell in his urine or faeces. His temperature feels normal, although I haven’t taken it with a thermometer, just by feeling his ears and body. His stomach doesn’t feel bloated, hard or painful and he doesn’t flinch when I run my hands over his abdomen. He will run up the field to say hallo and shares with another pig on the same regime who is completely fine.
When we got him a year ago he seemed to have an injury to his penis or sheath, there was a great deal of blood when he tried to serve the sow. We treated him with antibiotic and it seemed to clear up, he sired two litters and all seemed well.
So far all I have done is soak his food (12 percent protein pig nuts) and give him an extra ration of crab apples. I am tempted to make up a mixture of bananas and other fruit, maybe add a laxative, and see if that eases his bowel. Does anyone have any experience of purging a pig!? Senna?

I would give him some silage or haylage if you can get some and ease off on the dry nuts to see if that helps. Fruit/veg as well. I don't know your drinking arrangements, but does he have plenty to go at all day?

But don't leave it long before you take him to the vet. Probably a quick injection of a decent laxative is what he really needs.

Dear Simon,
thanks for your reply, I did call out the vet as I couldn't bear to see the poor chap in what looks like some discomfort. The vet prescribed a three day course of antibiotic injection and oral Buscopan. This is day three of the course and he's still straining.
He does have access to a rainwater trough ad lib in his field and an area of grass to browse although that is a bit tired looking now. There is a patch of fresh grass he can be let onto,do you think that would do as a substitute for silage or haylage? He's had a lot of windfall crab apples lately might that have upset his digestion do you think?